Method of monitoring an electrolytic cell

ABSTRACT

A method of employing wire reference electrodes in an electrolytic cell with at least one voltmeter to monitor the potential of the cell components and the cell is provided wherein the wire reference electrode comprises a lead-in wire portion, a reference wire portion, a sealing material to seal the junction of the lead-in wire reference portions, and a heat shrinkable insulating material.

This is a Continuation-in-part application of Ser. No. 631,427, filedJuly 16, 1984 now abandoned, which is a division of application Ser. No.373,204, filed Apr. 29, 1982, now U.S. Pat. No. 4,500,402.

BACKGROUND OF THE INVENTION

This invention relates generally to electrolytic cells and moreparticularly to wire reference electrodes and the method of utilizingwire reference electrodes to monitor voltage levels within the cell.

Typically the voltages of electrodes in either diaphragm type ofchloralkali electrolytic cells or the more recently developed filterpress membrane type of chloralkali electrolytic cells have been measuredby use of Luggin capillary tube that is positioned adjacent theelectrode and which passes through the cell housing or electrode frameto a reference electrode placed outside of the cell. Such a Luggincapillary tube is inserted through the cell wall on top of theelectrolytic cell by being passed through a polyethylene grommet orother appropriate seal and extended downwardly to a position adjacentthe center of the electrode, for example, a cathode. The Luggincapillary tube is then connected by a salt bridge or liquid junction toa separate calomel reference electrode situated externally of the cell.This system of measuring electrode voltages does not permit thepositioning of the reference electrode physically in the environment andat the exact location where the electrode potential to be measuredexits. This method of measuring electric potential for electrodes isbetter suited for laboratory testing where electrode potentials must bemeasured.

The use of Luggin capillaries in electrolytic cells that generate gasescreates further problems which are well known in the art. The Luggincapillary tube must have a continuous or unbroken stream of electrolytein the tube throughout its length. One proven method of initiallyachieving this is by drawing the electrolyte through the tube by asyringe or other type of suction device in order to have sufficientelectrolyte flow to obtain readings. However, gas generation createsbubbles that can block the relatively small capillary tube opening afterthe suctioning of electrolyte through the tube. This blockage, caused bythe nucleation and growth of bubbles around the mouth of the tube,blocks the flow of electrolyte and causes a break to occur in thecontinuous stream of electrolyte along the tube's entire length. Asimilar obstruction can be created merely by the transfer or depositionof bubbles from the solution which were caused by a high level ofagitation or rapid flow rate of the electrolyte fluid in the celladjacent the electrode surfaces. Additionally, concentrated electrolytesolutions can salt out or freeze in the tube, thereby blocking liquidflow through the tube. To avoid this, once the salt bridge isestablished additional dilute electrolyte is normally fed into the tube.

It is also possible that the continuous stream of electrolyte which mustbe maintained through the Luggin capillary tube to the saturated calomelreference electrode is not identical to the electrolyte to which theelectrode for which the potential is being recorded is exposed. Thisoccurs when the dilute electrolyte solution flow is maintaineddownwardly through the capillary tube from an external reservoir intothe cell electrolyte to avoid the gas bubble blockage at the tube'smouth or blockage within the tube from the aforementioned salting out ofelectrolyte. This flood of dilute solution does not permit an exactinitial voltage reading to be obtained since the dilution of theelectrolyte changes the measured voltage. In fact, this situationseverely limits the utility of Luggin capillaries in conjunction with asaturated calomel reference electrode since they typically provide apotential recording only for that short window of time when solution isflowing through the tube and are not suitable for continuous or extendedpotential measurements.

Any of these conditions affect the accuracy of the reading obtained fromthe reference electrode using a Luggin capillary and, in fact, mayobstruct the entire operation of the Luggin capillary.

Attempts to use Luggin capillaries in commercial electrolytic cells haveproven them not to be suitable for commercial operations because of thepractical problems encountered and their inherent limitations beyondthose already enumerated. For example, the occurrence of an alternatingcurrent (AC) signal or ripple in the plant power supply will createrapid voltage changes which cannot be sensed by Luggin capillaries.Although these rapid voltage changes are not necessarily detrimental tothe electrolysis, the potential in the Luggin capillaries cannot changerapidly enough and will, therefore, affect the reference electrode andits readings. Additionally, the length of the capillary tubes requiredfor commercial sized cells could extend to twenty feet in length inorder to connect to the external reference electrode. This length oftubing demands a very high internal pressure in order to keep thesolution flowing and sweep any gas bubbles out of the tubing. If thenecessary pressure to accomplish this is approached, the capillary tubestend to leak from cracks or other failures or they pop off of theirfittings. The latter event results in the spraying of hazardous causticor other electrolyte about the cell plant building.

An obstruction problem can also result where salt bridges or liquidjunctions are used with reference electrodes. These can become clogged,providing the same type of a problem encountered with gas bubbles in themeasurement of the potential and operation of the electrodes.

The desire to obtain electrical potential readings in the exact locationwhere the potential to be measured exists by the insertion of referenceelectrodes into the cell has created additional problems. The harsheffect on the reference electrodes of the electrolytes encountered whenthe reference electrodes are inserted within the cell has been apersistent problem affecting the durability of the materials used toconstruct these electrodes. The corrosiveness of the anolyte andcatholyte fluids tends to destroy the materials used. Referenceelectrodes with large diffuse Luggin openings also have been employed inattempts to avoid blockage problems. However, these electrodes have anelectrical resistivity that is not uniform about their exposed surface.This non-uniform resistivity results in erroneous measurements since thevoltage readings tend to be averages. This is especially true when theelectrodes are subjected to high voltage gradients. Attempts to solvethis problem have lead to the development of relatively costlystructures either with a separate reference electrode or theincorporation of the reference electrode into existing electrodes. Thesedevices utilize an annular element of porous material to close a cavitybetween the body portions of the reference and measuring electrodes tocreate an isolated cavity for the reservoir of electrolyte and areference junction of uniform resistance over all radial segments. Theability to incorporate these types of structures in the commercialelectrolytic cell has been difficult because of space requirements andthe costs.

The development of wire reference electrodes has provided an approachthat permits the electrode potentials to be monitored and recorded incommercial chloralkali electrolytic cells. However, prior wire referenceelectrodes have encountered the aforementioned durability problem,especially on the cathode side of the cell where the concentratedcaustic solution tends to dissolve the wire. This is especially true inwire reference electrodes wherein a platinized platinum wire isemployed. The dissolution because of the apparent high porosity of theexposed surface will occur over too short a period of time, often onlyseveral days, and limit the practical utility of these types ofreference electrodes in commercially operating cells.

It has also been found that the seal around the wire separating thelead-in wire from the exposed reference wire portion in the wirereference electrodes is critical. It has been discovered that ifelectrolyte, especially the caustic solution, leaks backwardly betweenthe exposed reference wire portion and the shielding that encases thelead-in wire, a second potential may be generated. This is particularlytrue at the weld point of the reference wire portion to the lead-in wirewhich is used so that the reference wire electrode may be connected overa substantially long distance to monitoring apparatus, such asvoltmeters, externally of the cell. Electrolyte solution wetting theweld joint will allow an electrochemical reaction, such as corrosion, sothat there will be one potential at the wire reference electrode andanother as a result of the reaction at the lead-in wire, despite the useof a polyfluorinated hydrocarbon insulating tube.

Where such reference wire electrodes have been utilized in the filterpress membrane type of chloralkali electrolytic cells there is thepotential for the electrodes to accidentally puncture the membranes,thereby reducing the efficiency of the cell operation. However, becauseof the utility of these wire reference electrodes to measure the totalcell voltage, the anode-to-reference electrode, referenceelectrode-to-membrane-to-reference electrode, and the referenceelectrode-to-cathode voltages, continued efforts have now resulted inthe solution of the aforementioned problems in the design of the presentinvention. This newly designed structure permits the electrodepotentials to be monitored over extended periods of time in commercialcells, as well as permitting fast transient studies of the operatingcell conditions to be made where Luggin capillaries and externalreference electrodes are not useful because of the high impedance levelpresent that distorts the output voltage signal.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improved wirereference electrode that will permit the extended monitoring of theanode, cathode, and membrane or separator voltage during operation incommercial chloralkali electrolytic cells.

It is another object of the present invention to provide a method formonitoring independently and determining the condition of the anode,cathode, and the membrane or separator in chloralkali electrolyticcells.

It is a feature of the present invention that the wire referenceelectrode utilized in conjunction with the anode is comprised of atitanium lead-in wire that is connected to a titanium dioxide-rutheniumdioxide coated titanium wire for measuring anode potential.

It is another feature of the present invention that the wire referenceelectrode utilized in conjunction with the cathode is comprised of atitanium lead-in wire that is connected to a palladium/silver alloy wirethat is a predetermined percent palladium and a predetermined percentsilver for measuring cathode potential.

It is another feature of the present invention that the wire referenceelectrodes are secured to the electrode surface in at least one locationvia an electrolyte-resistant thread.

It is a further feature of the present invention that an improvedheat-shrink material composed of an electrolyte-resistant outer sleevewith a fluorinated ethylene polymer (FEP) inner lining is applied to thelead-in titanium wire and a portion of the reference wire portion toprovide a durable, leak-resistant seal.

It is yet another feature of the present invention that the referencewire electrode is inserted into a foramen in the desired electrodeforaminous surface or into the electrode surface so that the referencewire portion is at least partly in the plane of the electrode surface.

It is an advantage of the wire reference electrodes of the presentinvention that the anode, cathode and membrane or separator potentialsmay be monitored independently to determine the condition of each cellcomponent by analyzing the anode-to-wire reference electrode, wirereference electrode-to-membrane-to-wire reference electrode, and wirereference electrode-to-cathode voltages.

It is another advantage of the present invention that the wire referenceelectrode may be positioned on an electrode surface so that it does notintrude into the electrode-membrane gap or may be employed in a cellwhere there is not a gap between the membrane or separator and electrodewithout puncturing the membrane or separator.

It is a further advantage of the present invention that the improvedheat-shrink seal employed avoids corrosion at the weld of the titaniumlead-in wire to the titanium dioxide-ruthenium dioxide coated wire orthe palladium/silver alloy wire.

It is another advantage of the present wire reference electrodes thatthey may be utilized for fast transient studies of cell operatingconditions where Luggin capillaries and separate external electrodescannot be employed because of distortion to the voltage signal due tohigh impedance values.

It is yet another advantage of the present invention that the wirereference electrodes can be employed in commercial electrolytic cells tomonitor performance of the individual cell components.

These and other objects, features, and advantages are obtained in themethod of employing the apparatus of the present invention wherein awire reference electrode having a lead-in wire of predeterminedcomposition, a reference wire portion of predetermined compositionconnected to the lead-in wire at a first location, sealing means andheat shrinkable means collapsible about the sealing means to prevent theleakage of electrolyte solution into the first location is utilized in aplurality of locations within an electrolytic cell in conjunction withat least one voltmeter to monitor the operation of the cell componentsduring extended operation.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages of this invention will become apparent upon considerationof the following detailed disclosure of the invention, especially whenit is taken in conjunction with the following drawings wherein:

FIG. 1 is an enlarged perspective view of a portion of a foraminouselectrode surface showing the wire reference electrode fastened thereto;

FIG. 2 is an enlarged sectional view taken along the lines 2--2 of FIG.1 illustrating the relative positioning of the exposed wire portion ofthe wire reference electrode and the electrode surface;

FIG. 3 is an alternative embodiment of the wire reference electrodeshowing the exposed reference wire portion that can be extended into aforamen of the foraminous electrode surface;

FIG. 4 is a graphical illustration showing the voltage values obtainedfor three electrolytic subcells during operation of a filter presselectrolytic cell to illustrate the monitoring value of such wirereference electrodes;

FIG. 5 is a diagrammatic illustration of the positioning of the leadsand the placement of the wire reference electrodes between an anodesurface, a membrane and a cathode surface in the method of monitoring anelectrolytic cell using one voltmeter;

FIG. 6 is a diagrammatic illustration of the positioning of the leadsand the placement of the wire reference electrodes between an anodesurface, a membrane and a cathode surface in an alternate method ofmonitoring an electrolytic cell to obtain direct potential readingsusing one voltmeter;

FIG. 7 is a diagrammatic illustration of the positioning of the leadsand the placement of the wire reference electrodes between an anodesurface, a membrane and a cathode surface in another alternate method ofmonitoring an electrolytic cell to obtain direct potential readingsusing four voltmeters; and

FIG. 8 is a diagrammatic illustration of the positioning of the leadsand the placement of the wire reference electrodes between an anodesurface, a membrane and a cathode surface in yet another alternatemethod of monitoring an electrolytic cell to obtain direct potentialreadings using three voltmeters.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The improved wire reference electrode will be discussed hereinafter inconjunction with its usage in a chloralkali electrolytic cell,especially in conjunction with the foraminous electrode surfaces of sucha cell. It is to be understood that the discussion of a foraminouselectrode surface is intended to encompass both anode and cathodesurfaces. It is also to be understood that the utilization of theimproved wire reference electrode of the instant invention, while beingdiscussed and exemplified in the context of a filter press membrane typeof chloralkali electrolytic cell, could equally well be applied to adiaphragm type of chloralkali electrolytic cell, or any other type ofelectrolytic cell where it would be of value to monitor electrodepotentials, providing that the specific metal composition selected forthe wire is compatible with the electrolyte solutions.

Looking at FIG. 1, there is shown a portion of a foraminous electrodesurface 10 with individual foramen 11. The electrode surface 10preferably is made from expanded mesh which is flattened. However, it ispossible to use an expanded mesh which is unflattened, or a perforatedplate, screen or other suitable materials. The composition of thematerial comprising the electrode surfaces is dependent upon whether ananode or a cathode is being discussed. The compositions are well knownin the art. For example, typical anode electrode surfaces are made oftitanium or tantalum with suitable coatings, while the cathode electrodesurfaces are made from nickel, iron, steel, or tantalum with suitablecatalytic coatings. The preferred composition traditionally has beentitanium for the anode electrode surfaces and nickel for the cathodeelectrode surfaces.

A wire reference electrode indicated generally by the numeral 12 in FIG.1, is shown in part. The wire reference electrode is shown having alead-in wire 14, which is shown in phantom lines. The lead-in wire 14 istypically made from titanium that is from about 20 to about 24 gauge.The lead-in wire is connected, such as by welding, at a location 15 tothe reference wire portion 16 of the wire reference electrode 12.

The reference wire portion 16 in the cathode chamber is constructed offrom about 20-24 gauge palladium/silver alloy wire. The alloy wire iscomprised of approximately 75% palladium and approximately 25% silverand its preferred thickness is 24 gauge. The exact range of thepercentages of palladium and silver which may be used in the referencewire portion 16 is variable. The operable composition of the referencewire portion 16 for a reference electrode purpose requires a minimumamount of silver to be present for the reason that will be explainedhereinafter. Therefore, it is felt that a range of percentages of silvergreater than 25%, as well as some finite percentage less than 25%, alsowill be suitable for the intended purpose. The palladium/silver alloyhas the advantage of being durable when immersed in or subjected to acaustic solution, as well as providing a steady potential during celloperation.

The palladium/silver alloy is know to absorb substantial amounts ofhydrogen and causes a potential shift from the reversible hydrogenpotential of approximately 50 millivolts in the environment of anelectrolytic cell. However, this is a one time only shift and thepotential, as previously mentioned, remains steady subsequent to theinitial potential shift, thereby providing a reliable potential read-outfor monitoring the cell operation. The presence of silver in the alloystabilizes the palladium and serves to lock it into a single phase. Thispreserves the predetermined crystalline phase of palladium after aninitial start-up procedure for charging the reference wire portion,which will be described hereinafter, is accomplished to build uphydrogen in the metal alloy. This charging of the palladium/silver alloyreference wire portion builds up the hydrogen which is absorbed in thesurface to form a palladium hydride at a stable level. This chargingprocess is particularly critical since in its absence it can take up totwo weeks to build up the steady state concentration of hydrogennecessary to form the stable palladium hydride potential.

The anode reference wire portion is from about 20 to about 24 gaugetitanium wire that has been appropriately coated. The preferred gauge is22 gauge wire. The conductive reference wire portion 16 is comprised ofa valve metal selected from the group consisting of tantalum, titanium,zirconium, bismuth, tungsten, niobium, and alloys thereof, such as forexample, the aforementioned titanium wire, that is coated with aruthenium chloride coating. The ruthenium chloride is used to produce aruthenium dioxide-titanium dioxide mixed-crystal material in accordancewith the teachings of U.S. Pat. No. 3,632,498, issued on Jan. 4, 1972,to H. B. Beer. The desired coating utilizes a mixed-crystal materialconsisting essentially of at least one oxide of a film-forming metal,such as titanium, and at least one oxide of a platinum group metal, suchas ruthenium. The ruthenium chloride coating solution suitable toproduce the desired ruthenium dioxide-titanium dioxide coating for thetitanium wire is, for example, as follows:

12.4 ml butanol

0.8 ml 36% HCl

6.0 ml Tetra-n-butyl-orthotitanate (C₄ Hg)₄ Ti

2.0 g.RuCl₃.

An exemplary preparation of the titanium wire is as follows. Theappropriately sized gauge titanium wire is cleaned with acetone and thenwashed with soap and water. The titanium wire is then etched withconcentrated (approximately 36%) hydrochloric acid (HCl) for 10 minutesand then rinsed with deionized water for about 10 to 20 minutes. Theruthenium chloride solution is applied to the titanium wire with a brushand fired in an oven from about 300° C. to about 500° C. from about 1 toabout 6 minutes, preferably at 400° C. for 5 minutes. This applicationand firing procedure is repeated four additional times. The titaniumwire is then heated in air at from about 300° C. to about 500° C. for 4to 8 hours, preferably at 400° C. for 6 hours. This produces the mixedcrystal coating necessary for a reference electrode to the used in ananode.

The reference wire portion in the cathode chamber, preferablyconstructed of 24-gauge palladium silver alloy, is welded to the lead-inwire 14 of the previously mentioned titanium or nickel. The exposedcathode reference wire portion 16 of the wire reference electrode 12 istreated, for example, by immersing in a 70% nitric acid solution forseveral minutes, generally 1-10 minutes, to clean the surface prior toinstallation in a cell.

Where a long electrical lead-in wire 14 is required, a nickel ortitanium wire, as appropriate is spot-welded at the weld location 15 tothe reference wire portion 16. The wire reference electrode 12 is thenready for sealing. The same procedure is utilized whether the wirereference electrode 12 is to be employed in an anode chamber or acathode chamber. The lead-in wire 14 is inserted within an electricalinsulator or tubing shield 18, preferably of polytetrafluoroethylene,such as that sold under the trademark Teflon®, that extends to a pointjust short of the weld location 15 where it junctions with an innerlayer of electrical insulator and sealant, preferably fluorinatedethylene polymer 19, hereinafter FEP. Atop and about the tubing shield18 and the FEP 19 is an electrically insulating heat shrink tubing 20,preferably formed from polytetrafluoroethylene such as that sold underthe trademark Teflon®. As seen in FIG. 1, the FEP 19 extends for a shortdistance outwardly from beneath heat shrink 20. Adjacent the terminousof the FEP 19 is the exposed reference wire portion 16 which is shown ashaving a dimple or indentation 21 where it extends into a foramen 11 ofthe foraminous electrode surface 10.

On the opposing side of foramen 11, the exposed reference wire portion16 is similarly sealed. An inner layer of FEP 19 surrounded with anelectrically insulating heat shrink material 20, such as theaforementioned polytetrafluoroethylene.

Once the wire reference electrode 12 is wrapped with the FEP 19, theinner tubing shield 18 and the heat shrink 20, it is placed in an ovenfor approximately 3 minutes at approximately 207° C. to melt the FEP andto cause the heat shrink tubing to collapse. After removing the wirereference electrode 12 from the oven and allowing it to cool, the wirereference electrode 12 is ready to be mounted to the appropriateelectrode surface. The wire reference electrode 12 is secured in placeby suitable binding means, such as polytetrafluoroethylene strings 22shown in FIG. 1 on opposing sides of the foramen 11 into which thedimple or indentation 21 extends. Alternate heating means, such as aGL-O-RING available from the Rush Wire Stripper Division of the EraserCompany, Inc. of Syracuse, N.Y. or a LUX-THERM Little Shrink,manufactured by the Hi-Shear Corp. of Torrance, Calif. may be used tomelt the FEP 19 and the heat shrink 20.

The sealing step is especially critical to the accuracy achieved withthe reference electrode. Both the tubing shield 18 that covers thelead-in wire 14 and the FEP 19 serve as electrical insulators to preventdistortion or erroneous signals from being transmitted back to recordingapparatus external of the cell when the wire reference electrode 12 isemployed. The heat shrink 20 also serves as an additional electricalinsulator. The FEP 19, however, primarily serves as a sealant to preventcaustic or other electrolyte from entering adjacent the exposedreference wire portion 16 and travelling upwardly to the weld at theweld location 15. If the caustic or other electrolyte leaks back up thewire to this location, inaccurate and distorted potential readings willresult. For example, caustic corrosion can occur at the location of thetitanium/silver palladium wire interface that will cause the titaniumweld to give a potential, but as a result of the titanium-causticcorrosion. There will also be a second potential at the exposedreference wire portion 16, the normal and desired location for measuringthe potential. The wire reference electrode 12 will then measure theaverage of the reversible half reaction 2e.sup. - +H₂ O⃡2OH⁻ +H₂ at thereference electrode and a nonreversible titanium corrosion reaction suchas Ti→Ti⁺⁺⁺ ±3e⁻ at the weld where the titanium wire is welded to thetitanium dioxide-ruthenium dioxide wire.

On the anode side if the electrolyte leaks back up into contact with thetitanium and the titanium dioxide-ruthenium dioxide interface at theweld location 15, this will cause a potential different from the normaland desired sensed potential at the exposed wire reference portion 16.The wire reference electrode will then measure the average of thereversible half reaction 2e⁻ +Cl₂ ⃡2Cl⁻ and the reference electrode andthe reaction 2e⁻ +Cl₂ →2Cl⁻ at the weld location 15 where the titaniumwire is welded to the titanium dioxide-ruthenium dioxide wire.

The caustic corrosion on the cathode side is especially a problem inprior wire reference electrodes that have attempted to use only apolyfluorinated hydrocarbon insulating tube. Experience has shown thatthis single polyfluorinated hydrocarbon insulating tube tends toseparate or develop small cracks along the length of the wire to whichit is applied, thereby creating entrance ways for caustic to back flowalong the reference wire to the weld location at the titanium and thepalladium/silver interface. In the instant invention, the multiplelayers of the electrical insulator and sealant FEP 19 and heat shrink 20prevent the wire reference electrode 12 from being exposed along itslength to caustic or other corrosive electrolyte that can corrode theinterface or weld.

The materials employed to electrically insulate and seal the weldlocation 15 of the wire reference electrode 12 are commerciallyavailable. The FEP 19 may be purchased separately from the ResinsDivision of E. I. DuPont de Nemours & Co. of Wilmington, Del. The tubingshield 18 may be purchased from Bel-Art Products of Pequannock, N.J. Theheat shrink 20 is available from Zeus Industrial Products, Inc. ofRaritan, N.J. Heat shrink with an already assembled FEP liner is alsocommercially available from Zeus Industrial Products so that individuallayers of FEP, heat shrink and tubing shield need not be applied. It ispreferred to use the ready made heat shrink 20 with the liner of FEP 19already inserted. Severe problems were encountered with the heat shrinktubing moving during the heating and shrinking process, especially whenthe FEP was separately wrapped about the wire in a very labor intensiveoperation. This movement exposed some wire to the caustic or othercorrosive electrolyte and created the opportunity for corrosion tooccur. Kynar® fluorinated vinyl polymer, available from PennwaltCorporation is also suitable for use as an insulator when brushed on thereference wire electrode 12 that is to be used in the anode. For thereference wire electrode 12 that is to be in a cathode, chlorinatedpolyvinyl chloride (CPVC) or polypropylene may be also employed as heatshrink material as suitable.

The positioning of the wire reference electrodes 12 adjacent to theappropriate electrode surface 10 affects the accuracy of the potentialreadings that are recorded. Along the edge of the electrode surfacesadjacent the electrode frame the voltage and current density may differfrom the more uniform voltage and current density over the rest of theelectrode surface. Also the non-uniform condition of the electrodesurface may cause redistribution of current and potential so that themeasured potential is nonrepresentative. This non-uniform condition ofthe electrode surface can be the result of leaching out of alloys, suchas aluminum or molybdenum, from the cathode surface and pitting in theanode surface. The placement of the wire reference electrode 12 at theedge of the electrode surface is normally not desirable because of thecurrent distribution edge effect which tends to cause an increase in thevoltage readings at this point.

Therefore, the preferred location for positioning the wire referenceelectrode 12 with respect to an electrode surface 10 to obtain a steadypotential reading has been determined to be approximately in the middleof the appropriate electrode surface along its horizontal dimension andabout 1/3 to 1/2 of the way up its vertical dimension. This verticalpositioning of the reference electrode tends to minimize the exposure ofthe electrode to product gas bubbles which affect the flow of thecurrent in the area adjacent the reference electrode. The current flowis affected since it must flow around bubbles and cannot go through thebubbles since each bubble creates a break in the continuity of theelectrolyte fluid. However, it should be emphasized that by positioningthe electrode preferably 1/3 of the way up the vertical dimension of theappropriate electrode surface, continuous and generally accuratereadings of the potential may be obtained at the desired location.

For wire reference electrodes 12 of the dimple style or design shown inFIG. 1, the ideal position is to place the dimple 21 into the potentialgradient between the anode surface and the membrane or separator, or thecathode surface and the membrane or separator, as appropriate. Byinserting the dimple 21 of the reference electrode into the diamondshaped space or foramen 11 in the mesh of electrode surface 10, as seenin FIGS. 1 and 2, and, therefore, into the potential gradient, the mostaccurate potential readings are obtained. Alternately, the referencewire electrode shown in FIG. 3, utilizing a straight exposed referencewire portion 16 wrapped within an FEP layer 19 adjacent a tubing shield18, both of which are covered with the heat shrink 20 over the area ofthe weld location (not shown), may be employed. In this embodiment, thewire reference electrode 12 is placed flat onto the mesh surface betweenthe electrode surface 10 and the membrane so it overlies the desiredforamen with the exposed reference wire portion 16 extending along thelonger axis of the foramen, which is seen in FIG. 1 to be generallyhorizontally.

Regardless of whether the dimple style of wire reference electrode 12 orthe straight style shown in FIG. 3 is employed, it has been found to beadvantageous to ensure that the exposed reference wire portion 16extends along the longer or major axis of the diamond shaped foramen 11.As just mentioned, this is seen in the instant case in FIG. 1 to begenerally horizontal. The wire reference electrodes 12 may be mounted inan electrolytic cell in several ways to obtain this orientation. Thewire reference electrode 12 may be tied to the front side of theelectrode surface 10 so that it is interposed between the electrodesurface 10 and the adjacent membrane or separator (not shown). It hasbeen preferred to secure the wire reference electrode 12 employing thedimple or indented style to the back side of the electrode surface 10 sothat the indentation or dimple 21 extends through one of the diamondshaped foramen 11, placing the exposed reference wire portion 16 inessentially the same plane as the electrode surface 10. This manner ofmounting is best exemplified in FIG. 2.

In addition it has been found with electrolytic cells using solid plateelectrodes that the exposed reference wire portion 16 or a suitablyshaped indentation or dimple 21 can be inserted into an appropriatelysized hole in the plate electrode so that the exposed reference wireportion is in the plane of the electrode. This positioning providesaccurate potential readings and can be used at a plurality of positionsabout the surface of the plate electrode, if desired, to monitor thepotential across the entire electrode surface during operation. Theholes can be drilled in the plate electrode at the desired positions tothe desired depths. Similarly with perforated plate electrodes it hasbeen found that an L-shaped exposed reference wire portion 16 can beused to position the wire reference electrode in the plane of theelectrode. The exposed reference wire portion 16 must be positioned sothat it rests generally in the center of the perforation, as must bedone with the drilled holes in the solid plate electrodes. The wirereference electrode must be secured in place along the electrode.

The wire reference electrode 12 is secured in place, regardless of thespecific mounting locations to the electrode surface by the use of thepolytetrafluoroethylene thread or string 22. Where the dimple orindented style of wire reference electrode 12 is employed, twopolytetrafluoroethylene threads or strings 22 are employed on eitherside of the exposed wire portion 16, as seen in FIGS. 1 and 2. Thismethod is desirable to anchor the wire reference electrode 12 assecurely as possible to the electrode surface 10 to prevent movement ordrift of the exposed reference wire portion 16 during cell operation.Such movement may be caused by tension on the lead-in wire or by theflow of the electrolyte and gas bubbles upwardly through the electrodesduring operation and is to be avoided because any repositioning of thewire reference electrode will affect the accuracy of any potentialreadings since the wire reference electrode will be moving with respectto the potential gradient. Should the exposed reference wire portion 16actually touch the electrode surface 10, the measured potential will, ineffect, be shorted out.

Alternately, the wire reference electrode 12 of the instant inventioncan also be separated from the appropriate electrode surface 10 byinstalling it next to the membrane or separator (not shown) by insertioninto a small groove in the gasket (not shown) that is employed betweenadjacent electrode frames so that the wire reference electrode 12 is onor closely adjacent to the membrane or separator.

In order to exemplify the results achieved, the following examples areprovided without an intent to limit the scope of the instant inventionto the discussion therein. The first three examples are intended toillustrate how comparison data can be obtained from operating cellsusing a wire reference electrode and the reliability or accuracy of suchdata.

EXAMPLE 1

An approximately 0.28 square meter pilot cell was operated atapproximately 3.0 KA/m² current density with approximately 32.0% sodiumhydroxide concentration at 90° C. The following voltage readings wereobtained:

    ______________________________________                                        Cathode vs. Pd/Ag      0.589  V                                               Anode vs. Ti           0.309  V                                               Pd/Ag vs. Ti           3.04   V                                               Total                  3.978  V                                               Cell (Measured)        3.94   V                                               ______________________________________                                    

EXAMPLE 2

An approximately 0.28 square meter pilot cell was operated atapproximately 3.0 KA/m² current density with approximately 33.7% sodiumhydroxide concentration at approximately 90° C. The following voltagereadings were obtained:

    ______________________________________                                        Cathode vs. Pd/Ag      0.571  V                                               Anode vs. Ti           0.305  V                                               Pd/Ag vs. Ti           3.10   V                                               Total                  3.929  V                                               Cell (Measured)        4.05   V                                               ______________________________________                                    

EXAMPLE 3

An approximately 0.28 square meter pilot cell was operated atapproximately 2.0 KA/m² current density with approximately 3.1% sodiumhydroxide concentration at approximately 90° C. temperature. Thefollowing voltage readings were obtained:

    ______________________________________                                        Cathode vs. Pd/Ag      0.325  V                                               Anode vs. Ti           0.160  V                                               Pd/Ag vs. Ti           3.28   V                                               Total                  3.773  V                                               Cell (Measured)        3.77   V                                               ______________________________________                                    

For each of the above examples, the measured cell voltage was obtainedby using a voltmeter that was connected to sampling leads or taps on thelead-in bus to both the anode and the cathode. The palladium/silverversus titanium reading represents the potential reading in the area ofthe separator or membrane. In this case, an ion-selective membrane,manufactured by E. I. DuPont de Nemours & Company and sold under thetrademark Nafion®, was inserted between each anode and cathode. Thesurfaces of the anodes and cathodes typically were catalytically coatedtitanium and nickel, respectively. Each cell used only one anode andcathode.

The cathode surfaces and the anode surfaces were referenced against theappropriate wire reference electrode, palladium/silver for the cathodeand ruthenium dioxide-titanium dioxide coated titanium for the anode.The wire reference electrodes 12 were of the dimple style and weremounted in the center of the diamond shaped foramen 11 in the meshelectrode surfaces 10 from the rear, as illustrated in FIGS. 1 and 2.The cathode versus the palladium/silver readings give the potential atthe cathode surface while the anode versus the titanium readings givethe potential at the anode surface. The palladium/silver versus thetitanium voltage readings give the potential at the membrane and weredetermined by measuring the potential between the two wire referenceelectrodes. In each case the sum of the voltage readings at the cathode,anode, and the membrane give a total that is essentially equivalent tothe measured cell voltage using a voltmeter, differing only from a highof 0.121 volts to a low of 0.003 volts. In the case of Example 3, alower total cell voltage was obtained when compared to the readingsobtained in Examples 1 and 2, but this was expected because of the lowercurrent density employed. The lower relative cathode and anode recordedvoltages combined with a higher membrane voltage in Example 3 wereprobably due to a shift in the reference electrode potential of one ofthe wire reference electrodes 12.

The significant fact, however, from all of the data is the accuracy ofreadings using reference electrodes when comparing the total cellvoltage obtained by summing the individual measured wire referenceelectrode reading to the cell voltage measured with a voltmeter.

EXAMPLE 4

An approximately 4 square meter filter press membrane chloralkali cellwas operated at approximately 3.0 KA/m² current density with a designedsodium hydroxide concentration of approximately 33.0% at 90° C. Thefilter press membrane chloralkali cell employed four ion-selectivemembranes, manufactured by E. I. DuPont de Nemours & Company and soldunder the trademark Nafion®, between adjacent anodes and cathodes. Eachend cathode was a half cathode so that each anode was sandwiched betweenadjacent cathodes. The surfaces of the cathodes included nickel and theanodes were made from titanium. Wire reference electrodes 12 wereinserted between each cathode surface and the adjacent membrane and eachanode surface and the adjacent membrane. This permitted the cathodesurface and the anode surfaces to be referenced against the appropriatewire reference electrodes; palladium/silver for the cathode andruthenium dioxide-titanium dioxide coated titanium for the anode. Thewire reference electrodes 12 were the dimple style and were mounted inthe center of the diamond shaped foramen 11 in the mesh electrodesurfaces 10 from the rear, as illustrated in FIGS. 1 and 2. The cathodeversus the palladium/silver readings gave the potential at the cathodesurface while the anode versus the titanium readings gave the potentialat the anode surface. The palladium/silver versus the titanium voltagereadings gave the potential at the membrane and included the potentialat the membrane and the electrolyte. These readings for three of thefour subcells are reflected in FIG. 4. A subcell is defined as a cathodesurface-membrane-anode surface grouping. Only three of the four subcellsare shown because the data for the fourth subcell was not reliablebecause of technical problems with the reference electrodes.

The voltage readings shown on the graph in FIG. 4 were obtainedutilizing the principles shown in the following equations:

    E Anode=(E.sub.oCl.sbsb.2 -E.sub.RE)+IR+OV

    E Cathode=(E.sub.oH.sbsb.2 -E.sub.RE)+IR+OV

    E Membrane=V.sub.IR +V[A-C]+(E.sub.RE cathode-E.sub.RE anode)

The voltage measured at the anode is equal to the potential of thereversible chlorine reaction at the anode minus the potential of thereference electrode plus the IR drop and the overvoltage necessary todrive the anodic reaction. The potential at the cathode is equal to thepotential of the reversible hydrogen reaction at the cathode minus thepotential of the reference electrode plus the IR drop and theovervoltage necessary to drive the cathodic reaction. The potential ofthe membrane and the electrolyte is equal to the potential drop acrossthe membrane plus the concentration difference potential of the anolyteand the catholyte fluids plus the difference of the cathode referencepotential and the anode reference potential.

The use of the reference wire electrodes of the instant invention in thecell enabled the operation of the cell to be monitored as a whole, aswell as through the monitoring of the voltage of the individualcomponents of the cell, to enable detection of any faulty components.The monitored three subcells are divided along the horizontal axis ofthe graph in FIG. 4 to show the results over 10 days of operation. Theanode voltage readings are shown on the graph of FIG. 4 by the darkenedcircles, the cathode voltage readings by the hollow rectangles orsquares, while the combined membrane and electrolyte voltage is shown bythe hollow triangles.

The data from subcell 1 shows high anode voltage in comparison to thesubcells 2 and 3. Concurrently, the membrane and electrolyte voltage andcathode voltage appear to be low in comparison to the other two subcellsshown. This is the pattern of voltage distribution that is to beexpected if the anode is not properly performing for some reason and hasan unusually high resistance. When this occurs, a filter press membranecell will distribute the total current among its subcells so that eachsubcell has the same voltage. If subcell 1 has a high resistance some ofits current will be portioned off to the remaining subcells.Accordingly, instead of experiencing the designed operating currentdensity of 3KA/m², the cell probably is experiencing a current densityof about 3.5 KA/m² in the two subcells which had normal resistance. Thiscurrent density is not obtained directly from the wire referenceelectrodes 12 of the instant invention, but may be found by comparingdata tables from the same sized cells where the recorded cathode voltageis the same.

The anode measurement for subcell 3 showed a drifted that started afterseveral days, but which did not affect the total cell voltage. The exactcause for this drift is unknown, but it is theorized that the anode wirereference electrode 12 was no longer at the reversible chlorinepotential.

When the operation of this particular cell was terminated and the cellwas broken apart, it was found that part of the electrical connection tothe first anode had failed and was the cause of the high anode voltage.Thus, by utilizing the wire reference electrodes 12 of the presentinvention, it was possible to diagnose the exact faulty component duringoperation. Previously where cell voltage, cell current, cell currentefficiency, and power consumption were used as indicators of cellperformance, only the condition of the cell as a whole could bedetermined. In instances such as the one specifically encountered inthis example, where one of the portions of the cell begins to fail dueto poor operation or faulty component, the operator previously couldonly guess at the nature and location of the problem in attempting tocorrect it. With the aid of the monitoring capability of the wirereference electrodes 12, it was possible to determine that the high cellvoltage was caused by the specific anode problem of subcell 1. This wasobvious because the expected anode voltage should have beenapproximately 0.4 or 0.45 volts, instead of the approximately 1.0 to1.05 voltage readings obtained.

Thus, it can be seen how monitoring the voltage of the individualcomponents of the cell can pinpoint problems that occur within the cellduring operation and enable quick replacement or correction of thedefective components.

FIGS. 5-8 show various configurations of voltmeters that may be employedto monitor the operation of an electrolytic cell, either manually orthrough the use of a computer which may be connected to controllers torecord data and actively adjust operating variables to achieve celloperation within the desired limits. The configurations illustrate howreadings can be used to directly provide the potential of the variouscell components or can be used, through simple mathematicalcalculations, to determine the potential of these cell components,depending upon the number of voltmeters employed. Significantly, wherethe configurations are used with computers, the cell monitoring methodmay be integrated into an overall cell monitoring system that is used tocontrol all aspects of a commercial electrochemical cell plantoperation. The membrane or separator is indicated as M in all Figures.

FIG. 5 shows a configuration with one voltmeter V that has one of itsleads move between relay Position 1, where a lead wire connects to afirst reference wire electrode X₁, positioned preferably in the plane ofthe cathode surface, relay Position 2, where a lead wire connects to asecond reference wire electrode X₂ positioned preferably in the plane ofthe anode surface; and relay Position 3 where a lead wire connects tothe anode. The other lead from the voltmeter V remains connected to thecathode. This method requires some mathematical calculations and is bestutilized in conjunction with a computer to perform the calculations anda single ended multiplex switch at each relay position.

The moving of the lead of the voltmeter V to relay Positions 2 and 3 isindicated by the dotted vertical arrow. The potential obtained from thereading of the voltmeter with the moving lead at each relay positionprovides an indication of the operating characteristics of the cell. Thereading with the movable lead at relay Position 1 gives the cathodevoltage, while the reading with the movable lead at relay Position 3gives the cell voltage or voltage across the cathode-membrane-anodespace. The membrane voltage is obtained from the difference of thereadings with the voltmeter movable lead at relay Positions 2 and 1. Theanode voltage is the difference of the readings with the voltmetermovable lead at relay Positions 3 and 2.

FIG. 6 shows a configuration employing one voltmeter with both voltmeterleads being moved to permit direct voltage readings to be obtained. Fourrelay positions are used with a lead wire at relay Position 1 connectingto the cathode, a lead wire at relay Position 2 connecting to a firstreference wire electrode X₁, positioned preferably in the plane of thecathode, a lead wire at relay Position 3 connecting to a secondreference wire electrode X₂, positioned preferably in the plane of theanode, and a lead wire at relay Position 4 connecting to the anode. Bymoving both leads of the voltmeter V direct measurements can be madewith a handheld voltmeter in a laboratory or to perform confirmationchecks on commercial membrane electrolytic cells. The best utilizationof the method shown in FIG. 6 is with a computer and double endedmultiplexer switches at each relay position.

Readings taken with the voltmeter V leads at relay Positions 1 and 2provide the cathode potential. Readings taken with the voltmeter V leadsat relay Positions 1 and 4 provide the cell voltage or voltage acrossthe cathode-membrane-anode space. Readings taken with the voltmeter Vleads at relay Positions 3 and 2 provide the membrane and surroundingelectrolyte voltage, while the anode potential is obtained by takingreadings with the leads at relay Positions 3 and 4.

The movement of the two voltmeter V leads between relay Positions 1 and3 and 2 and 4, respectively is indicated by the dotted vertical arrowsin FIG. 6.

FIG. 7 shows a configuration for monitoring the method of operation ofan electrolytic cell using four voltmeters to obtain direct potentialreadings without the need for multiplexer switches. "Hard" or directpermanent wiring connections or leads are employed at the cathode, thefirst wire reference electrode X₁, the second wire reference electrodeX₂ and the anode. Connecting the four voltmeters, V₁, V₂ V₃ and V₄, asshown permits simultaneous monitoring to take place. This is useful, forexample, where a repaired membrane or electrode is to be monitoredcontinuously. Use of a master switch control will permit this type of aconfiguration to "step through" multiple cells to obtain data readingssequentially in a commercial plant. This configuration may be usedwithout a computer to obtain full time data collection.

As seen in FIG. 7 voltmeter V₁ is connected to the cathode lead and thelead to the first wire reference electrode X₁ Voltmeter V₃ is connectedto the anode lead and the lead to the second wire reference electrodeX₂. Voltmeter V₂ is connected into the cathode lead wire and the anodelead wire, while voltmeter V₄ is connected to the lead wires for thefirst and second wire reference electrodes X₁ and X₂, respectively. Theconnections permit the cathode potential to be read at voltmeter V₁, theanode potential to be read at voltmeter V₃, the membrane and surroundingelectrolyte to be read at voltmeter V₄ and the cell voltage or voltageacross the cathode-membraneanode space at voltmeter V₂.

While the configuration shown in FIG. 7 is desirable, it should be notedthat not all voltmeters will permit tapping into the positive ornegative leads of another voltmeter in the manner that voltmeter V₄ hasbeen connected to the leads of voltmeters V₁ and V₃. This is based,apparently, on the operational amplifiers used within each type ofvoltmeter.

FIG. 8 shows another arrangement of three voltmeters that may beemployed to monitor the operation of an electrolytic cell by modifyingthe method shown in FIG. 7. Three voltmeters, V₁, V₂ and V₃, are used toas shown to obtain full time data collection, but with the necessity ofsimple mathematical calculations that make operation in conjunction witha computer desirable.

Specifically, the method shown in FIG. 8 connects voltmeter V₁ to theleads of the cathode and the anode. Voltmeter V₂ is connected also tothe cathode lead, as well as the lead of the first wire referenceelectrode X₁. Voltmeter V₂ then is connected to the anode lead and thesecond wire reference electrode lead X₂. Voltmeter V₁ then provides thecell voltage or cathode-membrane-anode space voltage. Voltmeter V₂provides the cathode potential and voltmeter V₃ provides the anodepotential. The potential of the membrane and the surrounding electrolyteis the difference of the V₁ reading and the sum of V₂ and V₃, or V₁ -(V₂+V₃).

It should also be noted that the wire reference electrodes utilized inboth the anode compartment and the cathode compartment can be reusedwith some maintenance between usage. For example, the palladium/silverwire reference electrode used in a cathode compartment should beimmersed in a 70% concentrated nitric acid solution for approximately 1to 5 minutes before being reused. The palladium/silver wire referenceelectrode also must be charged prior to use in a cell, whether theelectrode has been restored or is being used initially. This procedurerequires that after the electrolyte has been added to the electrolyticcell, the palladium/silver wire reference electrode 12 is connected tothe negative lead of a power source and the positive lead of the powersource to the cell anode. A charge of approximately 100 mA is maintainedfor approximately 10 minutes to charge the palladium/silver wirereference electrode while hydrogen evolves from the wire surface.

The ruthenium-chloride coated electrode that is utilized in the anodechamber requires no charging. However, this wire reference electrode canbe restored for normal use by cleaning with soap and water with a softbristle brush. If the ruthenium dioxide-titanium dioxide coating isscraped or worn off, however, the electrode must be recoated accordingto the procedure described in detail earlier, or discarded. If theruthenium dioxide-titanium dioxide coating is faulty or it is requiredto strip the old coating from the wire, this can be accomplished bysoaking the wire reference electrode in an Aqua Regia solution (75%HCl+25% HNO₃) for approximately ten minutes.

While the preferred structure in which the principles of the presentinvention have been incorporated is shown and described above, it is tobe understood that the invention is not to be limited to the particulardetails thus presented, but in fact widely different means may beemployed in the practice of the broader aspects of this invention. Thescope of the appended claims is intended to encompass all obviouschanges in the details, materials, and arrangement of parts, which willoccur to one of skill in the art upon a reading of the disclosure.

Having thus described the invention, what is claimed is:
 1. A method ofmonitoring the operation of an electrolytic cell having at least onecathode and at least one anode, each cathode and anode being sandwichedabout a separator and having anode and cathode surfaces, the methodcomprising:(a) placing a first wire reference electrode with a firstreference wire portion adjacent and between the cathode surface andseparator, the reference wire -; portion extending at least partiallyinto the plane of the cathode surface; (b) connecting a first voltmeterto the first wire reference electrode and the cathode; (c) placing asecond wire reference electrode with a second reference wire portionadjacent and between the separator and the anode surface, the secondreference wire portion extending into the plane of the anode surface;(d) connecting a second voltmeter to the second wire reference electrodeand the anode; (e) connecting a third voltmeter to the anode and thecathode; (f) recording a first potential reading of the cathode surfacefrom the first voltmeter; (g) recording a second potential reading ofthe anode surface from the second voltmeter; and (h) recording a thirdpotential reading from the third voltmeter; (i) determining thepotential of the separator and surrounding electrolyte from thedifference between the third potential reading and the sum of the firstpotential reading and the second potential reading.
 2. The methodaccording to claim 1 further comprising fastening at least one insulatedportion of the first wire reference electrode to the cathode surface. 3.The method according to claim 2 further comprising fastening at leastone insulated portion of the second wire reference electrode to theanode surface.
 4. The method according to claim 3 further comprisingfastening the second wire reference electrode approximately midwayacross the horizontal dimension of the anode surface and approximatelyone-third of the way up the vertical dimension of the anode surface. 5.The method according to claim 4 further comprising fastening the secondwire reference electrode to the anode surface withpolytetrafluoroethylene thread.
 6. The method according to claim 2further comprising fastening the first wire reference electrodeapproximately midway across the horizontal dimension of the cathodesurface and approximately one-third of the way up the vertical dimensionof the cathode surface.
 7. The method according to claim 6 furthercomprising fastening the first wire reference electrode to the cathodesurface with polytetrafluoroethylene thread.
 8. The method according toclaim 1 further comprising using a palladium/silver alloy for the firstreference wire portion.
 9. The method according to claim 1 furthercomprising using titanium with a ruthenium dioxide-titanium dioxidecoating for the second reference wire portion.
 10. The method accordingto c1aim 1 wherein the anode and cathode surfaces are foraminous with aplurality of foramens such that the method includes having the firstreference wire portion of the first wire reference electrode and thesecond reference wire portion of the second wire reference electrodeextending along and at least partially into a foramen in the cathodesurface and the anode surface, respectively.
 11. The method according toclaim 1 wherein the anode and cathode surfaces are plates withperforations such that the method includes placing the first referencewire portion of the first wire reference electrode and the second wirereference portion of the second wire reference electrode into aperforation in the cathode surface and the anode surface, respectively.12. A method of monitoring the operation of an electrolytic cell havingat least one cathode and at least one anode, each cathode and anodebeing sandwiched about a separator and having anode and cathodesurfaces, the method comprising:(a) placing a first wire referenceelectrode with a first reference wire portion adjacent and between thecathode surface and separator, the reference wire portion extending atleast partially into the plane of the cathode surface; (b) placing asecond wire reference electrode with a second reference wire portionextending at least partially into the plane of the anode surface; (c)connecting a voltmeter to the first wire reference electrode and thecathode; (d) recording a first potential reading of the cathode surfacefrom the first wire reference electrode; (e) disconnecting the voltmeterfrom the first wire reference electrode and connecting the voltmeter tothe second wire reference electrode; (f) recording a second potentialreading from the second wire reference electrode; (g) determining thepotential of the separator and surrounding electrolyte from thedifference between the first potential reading and the second potentialreading; (h) disconnecting the voltmeter from the second wire referenceelectrode and connecting the voltmeter to the anode; (i) recording athird potential reading; and (j) determining the potential of the anodeby subtracting the third potential reading from the second potentialreading.
 13. The method according to claim 12 further comprisingfastening at least one insulated portion of the first wire referenceelectrode to the cathode surface.
 14. The method according to claim 13further comprising fastening at least one insulated portion of thesecond wire reference electrode to the anode surface.
 15. The methodaccording to claim 14 further comprising fastening the second wirereference electrode approximately midway across the horizontal dimensionof the anode surface and approximately one-third of the way up thevertical dimension of the anode surface.
 16. The method according toclaim 15 further comprising fastening the second wire referenceelectrode to the anode surface with polytetrafluoroethylene thread. 17.The method according to claim 13 further comprising fastening the firstwire reference electrode approximately midway across the horizontaldimension of the cathode surface and approximately one-third of the wayup the vertical dimension of the cathode surface.
 18. The methodaccording to claim 17 further comprising fastening the first wirereference electrode to the cathode surface with polytetrafluoroethylenethread.
 19. The method according to claim 12 further comprising using apalladium/silver alloy for the first reference wire portion.
 20. Themethod according to claim 12 further comprising using titanium with aruthenium dioxide-titanium dioxide coating for the second reference wireportion.
 21. The method according to claim 12 wherein the anode andcathode surfaces are foraminous with a plurality of foramens such thatthe method includes having the first reference wire portion of the firstwire reference electrode and the second reference wire portion of thesecond wire reference electrode extending along and at least partiallyinto a foramen in the cathode surface and the anode surface,respectively.
 22. The method according to claim 12 wherein the anode andcathode surfaces are plates with perforations such that the methodincludes placing the first reference wire portion of the first wirereference electrode and the second wire reference portion of the secondwire reference electrode into a perforation in the cathode surface andthe anode surface, respectively.
 23. A method of monitoring theoperation of an electrolytic cell having at least one cathode and atleast one anode, each cathode and anode being sandwiched about aseparator and having anode and cathode surfaces, the methodcomprising:(a) placing a first wire reference electrode with a firstreference wire portion adjacent and between the cathode surface andseparator, the reference wire portion extending at least partially intothe plane of the cathode surface; (b) placing a second wire referenceelectrode with a second reference wire portion extending at leastpartially into the plane of the anode surface; (c) connecting avoltmeter to the first wire reference electrode and the cathode; (d)recording a first potential reading of the cathode surface from thefirst wire reference electrode; (e) disconnecting the voltmeter from thefirst wire reference electrode and connecting it to the anode; (f)recording a second potential reading across the anode and the cathode;(g) disconnecting the voltmeter from the cathode and connecting it tothe second wire reference electrode; (h) recording a third potentialreading of the anode; (i) disconnecting the voltmeter from the anode andreconnecting it to the first wire reference electrode so that thevoltmeter is connected to the first wire reference electrode and thesecond wire reference electrode; and (j) recording the potential of theseparator and the surrounding electrolyte.
 24. The method according toclaim 23 further comprising fastening at least one insulated portion ofthe first wire reference electrode to the cathode surface.
 25. Themethod according to claim 24 further comprising fastening at least oneinsulated portion of the second wire reference electrode to the anodesurface.
 26. The method according to claim 25 further comprisingfastening the second wire reference electrode approximately midwayacross the horizontal dimension of the anode surface and approximatelyone-third of the way up the vertical dimension of the anode surface. 27.The method according to claim 26 further comprising fastening the secondfirst wire reference electrode to the anode surface withpolytetrafluoroethylene thread.
 28. The method according to claim 24further comprising fastening the first wire reference electrodeapproximately midway across the horizontal dimension of the cathodesurface and approximately one-third of the way up the vertical dimensionof the cathode surface.
 29. The method according to claim 28 furthercomprising fastening the first wire reference electrode to the cathodesurface with polytetrafluoroethylene thread.
 30. The method according toclaim 23 further comprising using a palladium/silver alloy for the firstreference wire portion.
 31. The method according to claim 23 furthercomprising using titanium with a ruthenium dioxide-titanium dioxidecoating for the second reference wire portion.
 32. The method accordingto claim 23 wherein the anode and cathode surfaces are foraminous with aplurality of foramens such that the method includes having the firstreference wire portion of the first wire reference electrode and thesecond reference wire portion of the second wire reference electrodeextending along and at least partially into a foramen in the cathodesurface and the anode surface, respectively.
 33. The method according toclaim 23 wherein the anode and cathode surfaces are plates withperforations such that the method includes placing the first referencewire portion of the first wire reference electrode and the second wirereference portion of the second wire reference electrode into aperforation in the cathode surface and the anode surface, respectively.34. A method of monitoring the operation of an electrolytic cell havingat least one cathode and at least one anode, each cathode and anodebeing sandwiched about a separator and having anode and cathodesurfaces, the method comprising:(a) placing a first wire referenceelectrode with a first reference wire portion adjacent and between thecathode surface and separator, the reference wire portion extending atleast partially into the cathode surface; (b) placing a second wirereference electrode with a second reference wire portion adjacent andbetween the separator and the anode surface, the second reference wireportion extending at least partially into the anode surface; (c)connecting a first voltmeter to the cathode and the first wire referenceelectrode; (d) connecting a second voltmeter to the cathode and theanode; (e) connecting a third voltmeter to the anode and the second wirereference electrode; (f) connecting a fourth voltmeter to the first wirereference electrode and the second wire reference electrode; (g)recording a first potential reading of the cathode surface from thefirst voltmeter; (h) recording a second potential reading across thecathode surface and the anode surface from the second voltmeter; (i)recording a third potential reading of the anode surface from the thirdvoltmeter; and (j) recording a fourth potential reacting of theseparator and of the surrounding electrolyte from the fourth voltmeter.35. The method according to claim 34 further comprising fastening atleast one insulated portion of the first wire reference electrode to thecathode surface.
 36. The method according to claim 35 further comprisingfastening at least one insulated portion of the second wire referenceelectrode to the anode surface.
 37. The method according to claim 36further comprising fastening the second wire reference electrodeapproximately midway across the horizontal dimension of the anodesurface and approximately one-third of the way up the vertical dimensionof the anode surface.
 38. The method according to claim 37 furthercomprising fastening the second wire reference electrode to the anodesurface with polytetrafluoroethylene thread.
 39. The method according toclaim 35 further comprising fastening the first wire reference electrodeapproximately midway across the horizontal dimension of the cathodesurface and approximately one-third of the way up the vertical dimensionof the cathode surface.
 40. The method according to claim 39 furthercomprising fastening the first wire reference electrode to the cathodesurface with polytetrafluoroethylene thread.
 41. The method according toclaim 34 further comprising using a palladium/silver alloy for the firstreference wire portion.
 42. The method according to claim 34 furthercomprising using titanium with a ruthenium dioxide-titanium dioxidecoating for the second reference wire portion.
 43. The method accordingto claim 34 wherein the anode and cathode surfaces are foraminous with aplurality of foramens such that the method includes having the firstreference wire portion of the first wire reference electrode and thesecond reference wire portion of the second wire reference electrodeextending along and at least partially into a foramen in the cathodesurface and the anode surface, respectively.
 44. The method according toclaim 34 wherein the anode and cathode surfaces are plates withperforations such that the method includes placing the first referencewire portion of the first wire reference electrode and the second wirereference portion of the second wire reference electrode into aperforation in the cathode surface and the anode surface, respectively.